单线程情况下：
ConcurrentDictionary的写操作比使用锁的字典Dictionary要慢得多，而读操作要快一些。因此如果对字典需要大量的线程安全的读操作，ConcurrentDictionary性能比较好。
使用单线程时，并发字典ConcurrentDictionary性能不及Dictionary，但是扩展到5到6个线程，并发字典性能会更好。
class Program {
const string Item = "Dictionary item";
public static string CurrentItem;
static void Main(string[] args)
{
var concurrentDictionary = new ConcurrentDictionary();//线程安全集合
var dictionary = new Dictionary();//字典集合
var sw = new Stopwatch();
sw.Start();
for (int i = 0; i < 1000000; i++)
{
lock (dictionary)
{
dictionary[i] = Item;
}
}
sw.Stop();
Console.WriteLine("Writing to dictionary with a lock:{0}",sw.ElapsedMilliseconds);
sw.Restart();
for (int i = 0; i < 1000000; i++)
{
concurrentDictionary[i] = Item;
}
sw.Stop();
Console.WriteLine("Writing to concurrent with a lock:{0}", sw.ElapsedMilliseconds);
sw.Restart();
for (int i = 0; i < 1000000; i++)
{
lock (dictionary)
{
CurrentItem = dictionary[i];
}
}
sw.Stop();
Console.WriteLine("reading to dictionary with a lock:{0}", sw.ElapsedMilliseconds);
sw.Restart();
for (int i = 0; i < 1000000; i++)
{
CurrentItem = concurrentDictionary[i];
}
sw.Stop();
Console.WriteLine("reading to concurrent with a lock:{0}", sw.ElapsedMilliseconds);
Console.ReadKey();
}
}
